# Spermidine improves seed viability in Allium mongolicum by regulating AmCS-mediated metabolic and antioxidant networks

## TL;DR

Spermidine improves seed longevity in Allium mongolicum by boosting antioxidant and energy metabolism through a key gene called AmCS.

## Contribution

AmCS is identified as a pivotal gene in delaying seed aging, with a novel mechanism involving its interaction with AmPDK and regulation by spermidine.

## Key findings

- AmCS-overexpressing Arabidopsis showed 15.55% higher germination and increased antioxidant enzyme activity.
- AmCS overexpression reduced hydrogen peroxide and malondialdehyde accumulation by 35.20% and 40.40%, respectively.
- AmCS interacts with AmPDK to enhance TCA cycle flux and NADPH-dependent antioxidant capacity.

## Abstract

Seed deterioration involves oxidative damage and disrupted energy metabolism, yet the genetic mechanisms underlying aging resistance in Allium mongolicum remain unclear.

In this study, seeds primed with 0.8 mM spermidine (Spd) and stored for varying durations were subjected to transcriptome sequencing, targeted energy metabolite profiling, and assessments of antioxidant systems and energy metabolism enzymes.

We identified citrate synthase (AmCS) as a pivotal candidate gene involved in delaying aging processes. Under standard growth conditions, AmCS-overexpressing Arabidopsis lines exhibited a 15.55% higher germination rate compared to wild-type (WT), with enhanced activities of superoxide dismutase (SOD) and peroxidase (POD), and a 46.37% increase in ATP content compared to WT. Furthermore, these transgenic lines displayed significant reductions in hydrogen peroxide (H2O2; 35.20%) and malondialdehyde (MDA; 40.40%) accumulation. Mechanistically, AmCS-overexpressing Arabidopsis lines demonstrated heightened mitochondrial functionality, manifested as a 50.26% increase in cellular respiration rate and a 1.41-fold higher NADPH/NADP+ ratio than WT. Yeast two-hybrid assays validated the physical interaction between AmCS and pyruvate dehydrogenase kinase (AmPDK).

We demonstrate that the AmCS-AmPDK complex retards seed aging through two key mechanisms: (i) promoting acetyl-CoA flux in the tricarboxylic acid (TCA) cycle and (ii) enhancing NADPH-dependent antioxidant capacity through pentose phosphate pathway activation. Exogenous Spd activates this network by inducing AmCS expression. Our findings establish AmCS as a key genetic regulator for enhancing anti-aging traits in crop breeding, offering prospects for precision breeding and advancements in seed storage practices.